Not sure, but you will find out soon enough during the post message, right?

Anyway, i find that flashing is always a good idea, to get your firmware to the newest level as well as to remove the boot ROM if you don't need any of the disks connected to that controller for booting stage. This speeds up booting and prevents some BIOS issues with multiple controllers. This can be achieved simply by omitting the boot ROM file, only specifying the actual firmware. This is explained in documents like this one: https://www.servethehome.com/ibm-serveraid-m1015-part-4/

The 16-port LSI SAS controller is a good pick for compatibility. It is well supported and it offers a lot of ports on a single PCI-express slot, meaning it will be usable for a very long time until SAS/SATA drives become extinct. So i consider it a good investment, but a touch pricey. Though here and there it can be bought much cheaper than the regular retail channel for this product.

It is a touch more pricey than the LSI 16-port 9201-16 controller. But it has some advantages:

new 12Gbps SAS standard. It may not mean much for your SATA HDDs, unless you decide to use expanders where it will make a difference. This can really be a good investment if later on you might think about expanding even further with multiple pools that are all connected to the same controller, potentially some of them spun down. This controller can give you a long upgrade path where you continue to use it to supply your SAS expander with even more links in the future, hopefully when the 12Gbps SAS expanders will be cheaper too. So a good choice to invest in the future perhaps, if you have plans to expand even further later on.

PCIe 3.0 support. The new 12Gbps SAS controllers also bump from PCIe 2.0 to 3.0, meaning halving the effective latency for large transmissions and may impact performance somewhat, i am interested in how much.

And it has not 4 but 6 Mini-SAS connectors, for 24 SATA drives without the use of an expander. So that is quite a lot already. You might run into problems with power supply if you use a lot of disks though; make sure to invest in the right power supply and not one that spends much of its power exclusively to the graphics card cables, and has plenty of SATA cables to draw power from for your disks. I used the Corsair RM750x for my latest build.

Just make sure to use great care when inserting the Mini-SAS cables to the controller. I wrecked one of my IBM M1015 by fiddling in a narrow casing. I should have removed the controller from the PCIe slot and connected it then, instead. So lesson learned, hopefully i can warn others. ;)

Thank you! I got my two m1015 and going to flash them to IT mode. If I done that successfully I will move up to the bigger challange LSI SAS 9201-16i. Its my first time flashing so i'm a bit scared. Thanks! I will update when I'm done. :)

Remember to omit the -b parameter during flashing if you want to remove the boot Option ROM, meaning you cannot boot from any disk connected to that controller. The advantage would be that the boot goes faster and less chance of problems during BIOS phase. You can always turn it on later by flashing it again with the -b parameter present.

Use the latest firmware; remember that the firmware of the SAS controller is important, to stay compatible with the drivers. I do not know the details, but you ought to keep the driver and firmware version the same. ZFSguru uses very modern FreeBSD versions with the latest drivers, so it may also require the latest firmware on your LSI SAS controller.